Bake AO map from multires in Blender.2.82
I'd suggest another approach.

In the Shader editor, using Cycles, add Emission shader, add Input -&gt; Ambient Occlusion node and connect its AO output to Emission color input.
With viewport shading set to render tweak AO node's settings as you like.
In the Bake tab in Render Properties uncheck &quot;Bake from Multires&quot; checkbox and choose Emit as the Bake Type.


After that you can bake the result in a common way: create an image in Image Editor, choose it in Image texture in Shader editor, make sure the object is UV-unwrapped, active, and the Image Texture in the Shader editor is selected and press bake. As an emission shader is the only shader used, it bakes extremely fast.